1. Field of the Invention
The present invention relates to a torsion spring, an elastic device, and a sliding opening/closing apparatus and a portable appliance using the device, and more particularly to a torsion spring and an elastic device which are suitable for a sliding opening/closing apparatus of a portable appliance such as wireless phone, a PDA, and a PMP, etc. and a sliding opening/closing apparatus and a portable appliance using the same.
2. Description of the Prior Art
As consumers prefer apparatuses having a smaller thickness, it has been a problem in portable appliances to reduce thickness thereof.
FIG. 1 is a plain view illustrating a conventional sliding opening/closing apparatus, and FIG. 1 is an enlarged front view of a conventional torsion spring.
As shown, the sliding opening/closing apparatus 10 includes a guide member 12 having a guide part 11 formed therein, a slide member 16 movably installed in the guide member 12, and a torsion spring 20 rotatably assembled between the guide member 12 and the slide member 16. The torsion spring 20 is contracted while rotating depending on if the slide member 16 is moved along the guide part 11 by external force. Meanwhile, when the external force is removed, the torsion spring 20 is expanded while rotating so as to push the slide member 16 toward a longitudinal direction of the guide part 11.
As shown in FIGS. 1 and 2, a conventional torsion spring 20 is made in an integrally shape by winding a part of a spring wire 22 having a large amount of elastic force such as a steel wire, or by winding the part of a spring wire 22 while making a spiral shape thereof. The conventional torsion spring 20 includes a spiral part 24 formed by winding the spring wire 22 in a circular-shape or a spiral shape and a extension arm 26 extending toward an exterior of the spiral. A typical spring wire used for the torsion spring 20 of the sliding opening/closing apparatus 10 usually has a diameter thereof of 0.5 mm. So as to reduce thickness of the sliding opening/closing apparatus 10, a spring wire 22 having a diameter of 0.45 mm may also be used. When the torsion spring is made of a spring wire 22 having a diameter smaller than 0.45 mm, the amount of torsion moment which can push the slide member 16 decreases, and the torsion spring also tends while being inverted due to a vertical overlapping portion thereof. In this case, the torsion spring 20 generates a large amount of frictional force against the guide member 12 or the slide member 16 while rotating, thereby making it difficult to assemble. Such a torsion spring 20 can not be used in the sliding opening/closing apparatus 10.
Particularly, in the conventional torsion spring 10, the extension arm 26 is arranged in such a manner that the extension arm 26 is slanted from the spiral part 24 to the exterior of the spiral part 24 due to a vertical overlapping portion thereof. Because of this, when the extension arm 26 is rotated, one side portion of the spiral part 24 is naturally left. Because of this reason, an interval more than two times the diameter of the spring wire 22 is needed between the guide member 12 and the slide member 16. An interval as a space for typical operation needs to have a height as much as three times the diameter of the spring wire 22. This is an obstacle to reduce a thickness of a finished product such as a slide opening/closing apparatus 10 or a portable phone in which a slide opening/closing apparatus is installed.
Generally, an interval between the guide member 12 and the slide member 16 is kept to be a little more than two times the diameter of the spring wire 22 by considering the smoothly rational operation of the torsion spring 20. For example, if the diameter of the spring wire 22 is 0.5 mm, the interval between the guide member 12 and the slide member 16 has to be at least 1.5 mm.
Also, in the conventional torsion spring as shown in FIGS. 1 and 2, since the extension arm 26 extending from the spiral part is inevitably located out of the spiral part, it is difficult to wind up the torsion spring many times. If winding times decreases, dispersion of stress and elastic force caused by torsion moment of the spiral part are also reduced.